Question: Solve for $x$ and $y$ using substitution. ${x-2y = 12}$ ${y = x-5}$
Explanation: Since $y$ has already been solved for, substitute $x-5$ for $y$ in the first equation. ${x - 2}{(x-5)}{= 12}$ Simplify and solve for $x$ $x-2x + 10 = 12$ $-x+10 = 12$ $-x+10{-10} = 12{-10}$ $-x = 2$ $\dfrac{-x}{{-1}} = \dfrac{2}{{-1}}$ ${x = -2}$ Now that you know ${x = -2}$ , plug it back into $\thinspace {y = x-5}\thinspace$ to find $y$ ${y = }{(-2)}{ - 5}$ $y = -7$ You can also plug ${x = -2}$ into $\thinspace {x-2y = 12}\thinspace$ and get the same answer for $y$ : ${(-2)}{ - 2y = 12}$ ${y = -7}$